Generally, a gate of a MOSFET device is composed of a polysilicon material. Polysilicon is used because it satisfies a material feature required for a gate material, such as a high melting point, ease in forming a thin film and a line pattern, stability in an acidic environment, and a conformal surface thereof. Additionally, in an actual MOSFET device, the gate made of the polysilicon shows a low resistance because it contains a dopant such as, for example, phosphorous, arsenic, and/or boron.
However, as a level of integration of the MOSFET increases, there are limitations and drawbacks for implementing a resistance that is required between a narrow linewidth.
Using a conventional method for manufacturing a MOSFET device, it is difficult to form an ultra shallow junction that is required to a highly integrate MOSFET devices. Therefore, MOSFET fabrication requires a process technology to form an elevated source/drain region. Further, a control of a threshold voltage cannot be stabilized in the MOSFET device due to transformation of an implanted dopant array by an accompanying heat process.